1547 Bare Surface Heat Loss

It is often desirable to determine if any insulation is required and also to compare bare surface losses with those using insulation. Table 15.8 gives bare-surface losses based on the temperature difference between the surface and ambient air. Actual temperature conditions between those listed can be arrived at by interpolation. To illustrate, consider a bare, 8-in.-diameter pipe operating at 250°F in an 80°F ambient temperature. At = 250 - 80 = 170°F. Q for At of 150°F = 812.5 Btu/ hr-lin.-ft; Q for At of 200°F = 1203 Btu/hr lin. ft. Interpolating between 150 and 200°F gives